I am surprised that a hugh community and no one has the answer.
I am not a developer, but can give you a few things to try.
1. you can always contact Zebra Support Center and open a case
2. RFID SDK Kit is at this link - FX9500 Fixed RFID Reader Support & Downloads | Zebra
3. You can download and install the demo app session one or power session to test your reader and antennas to make sure they all are good. See the "Demos" section just below the SDK's.